1. Field of the Invention
The present invention is directed to a method of searching new writable address (which is referred to hereinafter as “NWA) for optical recordable medium, and more particularly, to a method of searching NWA having no repeatedly operated short seeking and following.
2. Description of the Prior Art
For every optical medium, regardless of CD-R or CD-RW, it is unavoidable to have to locate where the NWA for the next data recording operation is following the former data recording operation. Thereby, the optical pickup head will be able to move to the location of NWA in advance before the new data recording operation begins.
A widely-used optical recordable medium at least includes a plurality of sessions, which each includes a program area that further includes at least one program sub-area (track) therein. Tracks serve to record digital information. Taking the operation of writing packets to the tracks, for example, if the digital information recorded over the period of one data recording operation is not recorded to one complete track at once, the lead-in area of this optical medium will record the location of this track but has no knowledge of the information regarding where the NWA of this track is. Tracks of the optical medium are distributed in a spiral and successive manner, and, consequently, when it comes to beginning another recording operation, the searching for the location of NWA becomes very critical. Prior art methods at first move the optical pickup head to the area around the NWA (which is referred to hereinafter as “rough tuning.”), and after the step of rough tuning, move the optical pickup head with the method of so-called “fine-tuning,” so as to locate the accurate NWA. In other words, the optical pickup head will be moved to somewhere around the end of the recorded digital information in the former recording operation with the method of rough tuning, such as the method of locating a point midway between two reference points, at the very beginning in terms of “long seek.” However, the rough tuning should be executed only once due to the demand of less and less response time the optical pickup head is supposed to take as the latest information recording is going to be proceeded. The long seek at times is not necessary if the pickup head is not far away from the area where the digital information is recorded in last recording operation. Thereafter, operations of fine-tuning in terms of “short seeking” and “following” are going to be performed repeatedly, so as to locate the NWA.
Please refer to FIGS. 1A to 1C of illustrating a flow chart based on the prior art NWA searching method 50. The prior art method 50 includes steps of:
Step 51: starting steps of rough tuning;
Step 52: setting a first search starting point substantially equal to deducting the time duration preferably covering 75 blocks from the start time of the given track (the first predetermined rule);
Step 53: determining if this track is the end track of the program area, if not, go to Step 54, otherwise, go to Step 55 (the second predetermined rule);
Step 54: setting a search finishing point to be substantially equal to the end time of the track;
Step 55: setting the search finishing point to be the start time of the lead-out area of this session;
Step 56: determining if the difference between the search finishing point and the first search starting point is less than a first predetermined block time duration preferably equal to the time duration covering 100 blocks, if yes, go to Step 57, otherwise, go to Step 58 (the third predetermined rule);
Step 57: setting a second search starting point to be substantially equal to the first search starting point, and go to Step 59;
Step 58: setting the second search starting point to be substantially equal to the average of the first search starting point and search finishing point, and go to Step 61;
Step 59: finishing the rough tuning;
Step 61: determining if the pickup head is located at the blank area of the optical medium or not, if yes, go to Step 63, otherwise, go to Step 62;
Step 62: setting the first search starting point to be substantially equal to the second search starting point, and go back to Step 56; and
Step 63: setting the search finishing point to be substantially equal to the second search starting point, and go back to Step 56 as well.
FIG. 1A shows the flow of rough tuning as the NWA searching begins, which is followed by steps of fine-tuning, as illustrated in FIGS. 1B and 1C. The steps of fine-tuning include:
Step 74: starting steps of fine-tuning;
Step 76: determining if the pickup head is located on the blank area of this optical medium or not, if true, go to Step 77, or go to Step 78 instead;
Step 77: determining if the second search starting point is larger than the first search starting point, and then go to Step 79 if the consequence of above determination is true, otherwise, go to Step 80;
Step 78: assigning the present location of optical pickup head to the second search starting point and go to Step 81;
Step 79: finishing the fine-tuning;
Step 80: moving the pickup head to the location is substantially equal to having a fourth predetermined block time duration, preferably equal to the time duration covering 10 blocks, deducted from the second search starting point;
Step 81: determining if the second search starting point is less than the search finishing point, if yes, go to Step 76, and, otherwise go to Step 82;
Step 82: determining if the pickup head is on the end track at the present time, if yes, go to Step 84, otherwise, go to Step 83;
Step 83: setting the end time of the track as the NWA, and go to Step 89 thereafter;
Step 84: setting the start time of the lead-out area of the session as the NWA; and Step 89: end.
Steps shown in FIG. 1C follows steps of FIG. 1B include:
Step 91: searching the run-out blocks;
Step 93: setting the latest second search starting point with deducting 3 block time duration from the former second search starting point;
Step 95: starting to read the digital information from the latest second search starting point;
Step 97: moving the pickup head back and forth so as to locate the run-out blocks;
Step 98: setting the latest second search starting point as NWA; and
Step 99: finishing steps of fine-tuning.
As searching the NWA, this prior art method in advance has to figure out the range of searching, which theoretically should have the NWA therein, with setting the first search starting point and search finishing point. The location of pickup head eventually will converge to a second search starting point, which is supposed to be the NWA. There is no doubt that the second search starting point should lie between the first search starting point and search finishing point, given the nature that the second search starting point is the result of convergence of the first search starting point and search finishing point. In other words, the second search starting point should be later than the first search starting point but earlier than the search finishing point from the timeline aspect of the optical medium. However, because the first search starting point and search finishing point are consequences of firmware setting, it is possible at times that the timeline relationship between above three locations may not comply with the ideal timeline relationship for them. Therefore, the whole NWA searching firmware should include some precautionary measure, such as steps shown in FIG. 1B; so as to have the entire NWA searching process go on smoothly.
A conventional optical medium includes a plurality of sessions, each including a lead-in area, a program area, and a lead-out area, all of which are distributed thereon in this order. Digital information is recorded in the program area, which each includes at least one program sub-area (track). The first search starting point sometimes is the start time of one given track, but, as the given track is a blank track, the first search starting point should be a little bit earlier than the track start time. For ordinary skilled people in this art, it is very common to have a second predetermined block time duration (preferably the time duration covering 75 blocks) deducted from the track start time. However, it is noted that the value of second predetermined block time duration is the “end product” based on experiences of practitioners in this art. 75 blocks are equal to one second in Compact Disc (CD). While the blank track is the last track of this program area, the search finishing point is the end time of this track, as illustrated in Step 54; instead, the start time of lead-out area will be assigned to the search finishing point (Step 55).
Step 56 is to determine if the difference between the search finishing point and first search starting point is less than a first predetermined block time duration. The rough tuning serves to narrow the gap between the first start searching point and search finishing point. That is, as the difference is less than the first predetermined block time duration, meaning the following NWA searching will be performed much more smoothly, the whole process proceeds to Step 57 to set the second search starting point to be substantially equal to the first search starting point, and then to Step 59 to end the rough tuning; otherwise, the Step 58 will average the first start searching point and search finishing point, so as to set the averaged value to be the second search starting point (Step 58), and, thereafter, the whole process proceeds to Step 61. Theoretically, the difference between the above two reference points even both are configured by the firmware in advance will be narrowed down to be less than the first predetermined block time duration, which preferably is equal to the time duration covering 100 physical blocks, as long as only one Step 58 is performed.
Step 61 is for determining whether the pickup head is on the blank area or not. If so, the search finishing point will be reset to be the second search starting point (Step 63); otherwise, the second search starting point will be assigned to the new first search starting point (Step 62). Thereafter, the whole process returns to Step 56, and then to Steps 57 and 59, because it is apparent that the difference between the (new) first search starting point and search finishing point is not more than 100 block time duration again if they are only averaged once.
Step 74 in FIG. 1B starts the process of fine-tuning including determining if the pickup head at the present time is on the blank area or not (Step 76). If so, the fine-tuning process goes to Step 77, or Step 78. If Step 77, which determines if the second search start point is larger than the first search starting point, has a positive feedback, the fine-tuning will be terminated (Step 79). Otherwise, the whole process goes to Step 80, in which the second search starting point is moved back a fourth predetermined block time duration preferably covering 10 physical blocks, and then to Step 78, in which the current position of pickup head is read out, so as to assign this position to the latest second search starting point.
In the wake of Step 78, Step 81 further determines if the second search starting point is less than the search finishing point. If positive, the fine-tuning proceeds to Step 76, or to Step 82 instead to determine if the current location of the pickup head is at the end track or not. If the whole process goes to Step 82, there are two possible ways to determine the NWA, one of which is to assign the start time of lead-out area located behind the end track (program area) to be the NWA (Step 84), and the other one (Step 83) is to assign the end time of one given track—not the latest track—to be the NWA. Thereafter, both steps (Step 83 and Step 84) go to Step 89 to end the process of NWA searching.
However, the process of fine-tuning further includes steps of searching run-out blocks including moving the second search starting point 3 blocks back time-wise and starting to search run-out blocks. Still taking the packet writing for example, the specification book provides a link block, four run-in blocks, two run-out blocks, and several (generally being equal to 32) user-data blocks, all of which are measured on a one-block time duration basis. Over the period of searching the run-out blocks, the second search starting point is modified with a three-block adjustment each time, so as to avoid overlooking the run-out blocks. Step 95 tries to locate the run-out blocks through reading the current track from the second search starting point, and Step 97 adjusts the location of pickup head back and forth with a one-block adjustment, thereby assigning the latest second search starting point to the NWA (Step 98).
Apparently, Step 97 is necessary in this prior art method, especially while run-out blocks cannot be located in a very short period of time. Once this undesired condition happens, the pickup head inevitably has to be operated under the modes of short seeking and following, resulting in much more time spent on NWA searching and, therefore, slowing down the response time of optical medium players.